Production of metaldehyde



Pitented Nov. 27, 1928.

UNITED STATES PATENT OFFICE.

EMIL L'USGHER AlN'D HEINRICH STEIGER, BASEL, SWITZERLAND, ASQIGNORS TO THE FIRM: ELEKTRIZITKTSWERK LONZA, OF GAIIPEL AND BASEL, SWITZERLAND.

PRODUCTION or mrraLnEnYnE.

No Drawing. Original application filed .l'une lo, 1925. Serial No 36,278. and in Germany June 23, 1924.

Divided and this application filed July 22, 1926.

This application is a division of application Ser. No. 36,278 filed June 10, 1925, Patent No. 1,612,032.

The metaldehyde produced according to the U. S, Letters Patent No. 1,555,223 from metal salts and acids and pressed into cakes or press bodies is generally covered some time after lighting b a fine grey to black coating, which hin ers the combustion of the block. Research has now shown that the cause of this difliculty is to be found in the residue of the catalyst still remaining in the finished product, although the incombustible residueof the catalyst exists in the metaldehyde only in extremely small quantity, at most a few thousandths per cent, and consequently cannot by itself alone produce so much troublesome ash. It has also been found that several inorganic residues although con- 2 tained in much larger quantities in the metaldehyde donot affect the combustion to a noticeable degree. J

It follows therefore that this catalyst residue produces by-products by contact reac tion, which during the combustion, especially with insuflicient air supply, causes the forma tion of carbonaceous slag films on the metaldehyde block, which after the combustion have a dry or grey appearance. l hese difficulties cannot be removed by a further purification of the metaldehyde, because that would involve almost insuperable difliculties.

We havenow discovered that these difliculties do not occur or only occur to a very Serial No. 124,288.

slight extent if in the production of metaldehyde fromacetaldehyde, substances are used as catalysts which during the combustion process evaporate, burn themselves or are separated into their constituent parts, which do not act prejudicially on the unburnt metaldehyde and which at the same time, es-

pecia-lly with the use of an excess of acid according to the aforesaid patent, quickly furnished a very good yield of metaldehyde, especially if the catalyst and the acetaldehyde are both used in as waterfree a condition as possible; To this type of catalyst belong salts which result from the action of strong acids on inorganic nitrogen bases, for example: ammonium bromide, hydrazine ch loride and hydroxylamine,

The catalyst can be added in the form of a neutral or acid salt, or can itself be roduced in the reacting material, the aceta dehyde being first treated with the base and then with the necessary quantity of acid.

What we claim is: r g

'A process for'the production of metaldehyde which burns practically free from soot and ash, consisting in treating acetaldehyde with such catalyzer salts that result from the action of strong acids on inorganic nitrogen bases.

In witness whereof we have hereunto signed our names this 7th day of July, 1926.

EMIL LUSCHER (HEINRICH STEIGER. 

